1. Field of the Invention
The present invention relates to a semiconductor memory, for example, a nonvolatile semiconductor memory such as a NOR flash memory including a reference current generating circuit.
2. Background Art
A NOR flash memory of the prior art includes, for example, a reference current generating circuit for supplying a reference current to a sense amplifier (for example, see Japanese Patent Laid-Open No. 2004-103211). The reference current generating circuit includes, for example, a reference cell, a current mirror circuit connected to the reference cell, and an output section which is fed with a current obtained by current mirroring a current passing through the reference cell from the current mirror circuit.
In the reference current generating circuit, for example, the initial potential of the reference current is a ground potential at the output section. Then, the output section is charged by a MOS transistor making up the current mirror circuit.
An amount of charge required for charging is determined by a potential difference (the ground potential−a direct-current potential reached by the output section)×a parasitic capacitance. In this case, charging from the current mirror circuit is interrupted by the discharge of an output MOS transistor which makes up the output section and is diode-connected.
Thus, the closer to the direct-current potential reached by the output section, the longer the discharge time. In other words, in the prior art, the rate of rise of the reference current cannot be increased.